142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

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168 K. Ito, S. Kawaguchi the polymerization include monomer, water, surfactants, and initiators. Upon mixing, the surfactant molecules cluster into micelles and their hydrophobic cores are swollen with monomer. Their diameters are typically of the order of 50–150 Å, and their number density is of the order of 10 17 –10 18 dm –3 . The bulk of the monomer, however, exists in the form of large-size droplets with surfactant molecules adsorbed on their surfaces; their diameters are typically in the range of 1–10 µm, and their number density of the order of 10 9 –10 11 dm –3 . Therefore, the polymerization is believed to take place in the micellar phase, the aqueous phase, the monomer droplet phase, and the particle phase. Three major mechanisms have been proposed for particle formation in emulsion polymerization – micellar, homogeneous, and droplet nucleation – depending on the surfactant concentration, the monomer solubility in the aqueous phase, and the extent of subdivision of the monomer droplets. This has been a central subject in the emulsion polymerization for a long time and is still a controversial issue. Instead of conventional surfactant molecules, amphiphilic water soluble macromonomers, especially PEO macromonomers, have been used extensively as a reactive emulsifier and as steric stabilizer polymer, as summarized in Table 5. Generally speaking, however, the mechanism for the particle nucleation in the emulsion polymerization systems using macromonomers has been poorly established when compared to the dispersion copolymerizations with macromonomers as mentioned earlier. The first work on the emulsion copolymerization with a macromonomer has been reported by Ito et al. [132] for styrene using PEO macromonomer 49. Subsequently, several research groups have reported the synthesis and some properties of latex particles containing PEO chains from 26, 27, 36, 50–52, attached to their particles surface [132–140]. Ottewill and Satgurunathan [134] and Westby [135] reported the preparation of such particles in a multistage emulsion po- Table 5. Examples of emulsion copolymerization with macromonomers Macromonomer Monomer Ref. PEO, 49 Styrene 132 PEO, 36 Styrene 133 PEO 27b Styrene 134 PEO 27b Butyl acrylate 135 PEO 50 Styrene 136 PEO 26 (m=7) Styrene 137 PEO 26(m=1, 11), 27a(m=10), 27b, 51, 52 Styrene 138 PEO 27a (m=11) Styrene 139 PEO 26(m=1, 4, 7) Styrene 140 POXZ 34 Styrene 143 POXZ 53 Styrene 144 POXZ 54 Styrene 145 POXZ 55 Vinyl acetate 146 PMA 48 Styrene 127
Poly(macromonomers), Homo- and Copolymerization 169 lymerization process in which PEO macromonomer 27b was introduced in the final stage. These latexes were extremely stable to the addition of electrolyte and to the freeze-thaw [141]. Winnik et al. [142] have examined the influence of such surface grafted PEO chains on the latex film formation of PBMA latex particles by using nonradiative energy transfer method. (49) (50) (51) (52) Kobayashi et al. [143–146] have synthesized several types of amphiphilic poly(2-oxazoline), 34 and its block cooligomers, 53–55, and applied them to soapfree emulsion copolymerization of styrene and vinyl acetate to produce monodisperse, submicron-sized latex particles. They found that the particle size significantly depended on the type of macromonomer used and generally decreased with increasing the macromonomer concentration. (53) (54) (55) The latex particle diameter produced in the emulsion copolymerization of styrene with partially neutralized poly(methacrylic acid) macromonomers, 48, was studied as a function of degree of neutralization [127]. The latex particle
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142 Advances in Polymer Science Edi
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Branched Polymers I Volume Editor:
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Volume Editor Dr. Jacques Roovers I
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Preface While books have been writt
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Contents Synthesis of Branched Poly
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Synthesis of Branched Polymers by C
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72 N. Hadjichristidis, S. Pispas, M
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100 N. Hadjichristidis, S. Pispas,
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Page 137 and 138: Poly(macromonomers): Homo- and Copo
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Dendrimers and Dendrimer-Polymer Hy
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Author Index Volumes 101-142 Author
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Author IndexVolumes 101-142 231 Dun
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Author Index Volumes 101-142 233 Ka
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Author Index Volumes 101-142 235 Og
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Author Index Volumes 101-142 237 Su
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Subject Index Addition-fragmentatio
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Subject Index 241 Microphases 11z,
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